Cellular wireless is an increasingly popular means of personal communication in the modern world. People are using cellular wireless networks for the exchange of voice and data over cellular telephones, personal data assistants (“PDAs”), cellular modems, and other devices. In principle, a user can seek information over the Internet or call anyone over the Public Switched Telephone Network (“PSTN”) from any place inside the coverage area of the cellular wireless network.
In a typical cellular wireless system, an area is divided geographically into a number of cell sites provided by a radio access network (“RAN”). The RAN typically comprises one or more base transceiver stations (“BTSs”), each of which has one or more antennas that radiate to define a radio frequency (“RF”) radiation pattern. The BTS(s) of the RAN may then be coupled with a base station controller (“BSC”) or radio network controller (“RNC”), which may in turn be coupled with a telecommunications switch or gateway, such as a mobile switching center (“MSC”) or packet data serving node (“PDSN”) for instance. The switch or gateway may then provide connectivity with a transport network, such as the PSTN or the Internet for instance.
When a mobile station (such as a cellular telephone, a wirelessly equipped PDA or personal computer, or another suitably equipped device) is positioned in a cell, the mobile station communicates via an RF air interface with the BTS of the cell. Consequently, a communication can be established between the mobile station and another entity, via the air interface and the RAN.
Most cells in a wireless network are usually further divided geographically into a number of sectors (which can be visualized ideally as pie pieces), each defined respectively by radiation patterns from directional antenna components of the respective BTS, or by respective BTS antennae.